Nothing personal, Ken123, but it sounds like you haven't run this idea past any friends who work with HVAC systems.
- You have to remember to manually press a button every time you change zones.
- 2/3rds of the registers closed whenever the system is running = extremely inefficient.
- If you don't go into a zone for several hours the temperature in the zone will probably take a long time to reach a comfortable level.
Seems like you'd be better off with an approach like this:
1. Have all three thermostats working at the same time. (no manual switching)
2. If any of the three thermostats is out of limits, switch on the HVAC.
- If the thermostat for a zone is out of limits, open the baffle(s) in that zone.
- If the thermostat for a zone is within limits, close the baffle(s) in that zone.
- Once all three thermostats are within limits, switch off the HVAC.
3. Add day/time-based temperature settings. (optional)
- You don't need to heat/cool the house as much while you're at work.
- Cool the bedroom zone shortly before your normal bedtime.
Scott